Transformer cooling system control



May 26, 1953 ,H h 1:, I A I A f I I I NN Nah O y ll|l|||l mm nfl lllll -lll l a 2 fi m :1 mm o m 9 H mm mm INVENTOR i e h 0 u H V r U h I r A BY A WITNESSES: 1

Patented May 26, 1953 UNITED STATES PATENT OFFICE TRANSFORMER COOLING SYSTEM CONTROL 3 Claims.

The invention relates to transformers, and, more particularly, to means for protecting aircooled, air-insulated transformers, from excessive temperatures.

In Patent No. 2,223,530 issued to H. V. Putnam and assigned to the same assignee as the present application, protective means is provided for electrical apparatus such as a transformer, the protective means including a control device responsive to predetermined operating conditions of the apparatus. More specifically, the control device operates to actuate an indicating device when the operating condition of the transformer hasattained a predetermined value and operates to disconnect the transformer from the line when the operating condition of the transformer has attained a slightly higher predetermined value. Such protective device is commonly employed in oil-cooled transformers.

Where attempts have been made to employ such protective devices in air-cooled transformers to control the operation of a cooling fan, it has been found that the thermal variations encountered produced an irregular operation of the cooling fan. For example, if a transformer is operating under overload conditions, the thermally responsive means, which is ordinarily a bimetal element incorporated within the control device, will operate to move in a predetermined direction for actuating the fan. The operation of the fan will impart a cooling effect not only to the winding of the coils, but also to the thermally responsive device, thereby effecting an actuation of the bimetal element in the opposite direction to effect the deenergization of the fan. Since the transformer will not have been sufiicien'tly coo ed by the short operation of the fan, the thermally responsive device will immediately be actuated once more to its predetermined position for again effecting the operation of the fan. This cycle of operation will, therefore, continue indefinitely, resulting in the improper operation of device thereby reducing the effectiveness of the forced cooling and increasing the switching on the circuit controlling contact members.

An object of the invention is to provide an ai -cooled, air-insulated electrical transformer r protective means including a control depcrative in response to predetermined conditions of the transformer for selectively actuating plurality of safety and indicating devices disposed. for preventing damage to and indicating operating conditions of the transformer.

Another object of the invention is to provide protective means for air-cooled, air-insulated electrical transformers, including a control device operative in response to predetermined conditions of the transformer for actuating a cooling means upon the occurrence of a predetermined operating condition of the transformer and thereafter actuating a signalling device upon the occurrence of other predetermined operating conditions of the transformer.

A further object of the invention is to provide an air-cooled, air-insulated electrical transformer having protective means, including a control device responsive to operating conditions of the transformer to control the sequential operation of a plurality of contactors and thereby control the operation of a cooling device and indicating means associated with the transformer and to provide for thereafter maintaining the contactors in operating position independently of the operation of the control device in response to the operation of the cooling device.

Other objects of the invention will become apparent from the following description when taken in conjunction with the accompanying drawing, the single figure of which is a view in side elevation and partly in section and partly diagrammatic, of apparatus and circuits illustrating an embodiment of this invention.

Referring to the drawing, this invention is illustrated by reference to an air-cooled, airinsulated transformer I which is of the general construction described and claimed in Patent No. 2,295,415 to G. R. Monroe, issued September 8, 1942, and assigned to the same assignee as this application. As illustrated, the transformer comprises a casing 2 which may have wire mesh side walls (not shown) for providing free access of the surrounding air to contact a core struc ture and winding structure thereon, disposed within the casing. The core structure 3 is provided with two vertically positioned winding legs and a connected by two horizontal yoke portions clamped between channel members ii at the top of the structure and between channel members i at the bottom of the structure, respec tively. and held in position by bolts 8 for clampthe channel members together. A pair of upper pressure plates or rings and a pair of lower support members it, respectively, are provided for assisting in holding a high-voltage winding ll and a low-voltage winding 12 disposed internally thereof in their proper positions about the winding legs 4 and 5 of the core structure 1. The rings 9 and support members It are of a spider construction (not shown) to facilitate pas- 3 ge of air therethrough to and from the windi2 and H.

The low-voltage winding 1 comprises a plu rality of cylindrical coils l3 separated by spacers and wound about a central tube 85, the tube and coils #3 extending from the lower support member 53 to the upper pressure plates 9. The high-voltage winding ll comprises a plurality of flat or disk-type coils ES separated by spacers ll of insulating material, such as porcelain, the spacers I? being arranged in vertical columns between adjacent coils and the spacers E l being arranged in horizontal rows between adjacent coils. The spacers H and I4 are spaced about the circumference of the windings H and 5:2, respectively, in a manner to provide openings in the windings H and I2 radially between the adjacent coils, the spacers I =1 providing openings '5 between the coils E3 of the winding 12 which extend from the lower support members it to the upper pressure plates F3 for permitting the free inovelnent of air currents upwardly between the coils The windings H are positioned between bloclis between the support members it and the lower end of the windings H and between the pressure rings Q and the upper end of the windings H to assist in clamping the coils of the windings H firmly in place between the members 6 and.

In order b provide for forced cooling of the core and coil assembly, a fan IS is disposed at one end of a housing 2 for operation when the transformer is operating under a predetermined overload condition. As illustrated, the housing Ed is positioned beneath the coil assembly of the transformer I, the upper horzontal surface of the housing 726 constituting the support members if} extending below the coil assembly for supporting the coil assembly as described hereinbefore, the lower horizontal surface of the housing 2-8 constituting a lower plate member 25 for supporting the channel member I, one end of the housing terminating in an opening 22 for receiving the fan the housing 28 being enclosed by supporting side wall The plate member it! is formed with a central opening (not shown) for receiving to lower ends of the winding legs and 5 of the core structure 3, as viewed in the drawing, opening in cooperation with the sp r construction (not shown) of the plate permitting cu en-ts forced upwardly operation of the fan i? to enter into the region occupied by the coil assembly for circulation thereabout cool the coil assembly.

In order ol the operation the which for actuation upon occurrence of a p-..det r'.iined operating '1 of the transformer i for cooling the coil and to also control the opera g device which n i be a suitable device dispc r to indicate predetermined e transfor'ae within casing 2. wh ch is prereracl mounted -.top coil ass. i the transformer i on one of sure plates and over one of the spider opentherein. The control device is of the construction of and opera" larly to the (3 describ d P tent No. 2,169,586 to M. G. Leonard, issue 15, 1939, and assigned to the same assignee as this application.

A thermally responsive binietal element 23 is included in the control device and comprises operating cond control devic lllgS a part of a circuit which extends from. one terminal of a or ent transformer 26 disposed in inductive relatcn with a condictcr 3B of the load circuit of the transformer i, through the bimetal con-z: ctor ergizing winding 32 of a relay 53, a -o the other terminal or" the cu The bipresence of da? ich might overh. t transformer i. the UL" to predetere low-volthas become ovcrheatc'l by the erous overloads on the tra sformer v. ich cause cur; air to rise upwa. 5' between the c o the easof the thermally respo vice 25.

In order to prev the fan i9, the ene is includ described hereinheicre. The v =iore, responl to the load d signed and ed thereTJ-y when the load attains value of the rat :1 full load current a I the contact met 1 er ing position.

tel 'roin the power line conductor an autowhich ex: conductor through 1natie-1nanual selec in automatic p and conductor to the control device 22' In order to control the sequential operation of a, plurality of contactors to thereby control the operation of the fan l9 and the signal device 2 3, a pair of pivotally mounted switch operating members 4| and 42 are included in the control device within the casing 25. The member 41' is disposed to be engaged by the bimetal 28 upon the occurrence of a predetermined movement of the bimetal 28 to the right to effect movement of the free end of the member II to the left. A contact member 43 carried by the member M at the free end thereof is thereby moved into engagement with a cooperating fixed contact member for establishing a circuit extending from power line conductor 36 through conductor 31, switch 38, contact member 35, conductor as, contact members 40 and 43, conductor M, the energizing winding 45 of a contactor 4 and conductor 41 to the power line conductor 45. The winding 45 of the contactor 46 is, therefore, connected across the power line conductors 35 and 4'8 and is thereby energized to simultaneously effect movement of a plurality of contact members 49, 50 and 5| thereof to circuit closing nos-F cus.

Movement of the contact members 53 and SI to circuit closing positions effects energization of the fan motor 52 through a circuit exten ing er i5, .ieznbcr Q5: of

from power line conductor 38 through conductor 53, contact member 50, conductor 54, fan motor 52, conductor 55, contact member 5| and conductor 41, to the power line conductor 43, thus effecting the energization of the fan motor 52 to operate the fan I52. Movement of the contact member 49 effects establishment of a holding circuit for the winding 45 of the contactor 48 which is disposed to thereafter maintain the energization of the fan motor 52. Such holding circuit extends from the power conductor 36, through conductor 31, switch 38, contact member 35, concluctor 58, contact member 49, energizing winding 45 of contactor 46 and conductor 41 to the line conductor 48.

The holding circuit is necessary for the effective operation of the protective device for, as the fan l9 begins operation, air is forced upwardly thereby from the housing and is circulated about the area occupied by the overheated lowvoltage windings l2 to force the air heated by the windings I2 upwardly into the casing 2.5 for not only cooling the low-voltage windings 52 but for also cooling the thermally responsive bimetal element 28. It is readily apparent that such a result is inevitable, for the air actuated by the fan l9 rises upwardly from the low-voltage windings l 2 into the casing 26 to effect such cooling of the bimetal element 28. The thermal action of the cooler air on the bimetal element 23 tends I.

to cause the bimetal element 28 to operate to reverse the initial sequence of operations whereby the free end of the switch operating member 4| tends to move to the right to disengage the contact members and 43 and interrupt the its energized circuit closing position to thereafter maintain operation of the energizing circuit for the fan motor 52 independently of the position of the bimetal element 28. However, when the load current on the transformer l is reduced to a predetermined value which permits safe operation of the transformer I, the current flow through the winding 32 of the relay 33 is insufficient to maintain the relay 33 in a circuit closing position and the contact member 35 drops to a circuit interrupting position to interrupt the holding circuit for the winding of contactor 46.

In order to control the operation of the signal device 24 another contactor 51 having an energizing winding 58 is included in the control circuits for the protective means. When the transformer I is initially set up for operation, the winding 58 is placed in a normally energized condition by manual actuation of a start-reset switch 59 to a circuit closing position for establishing a circuit extending line conductor 36 through conductor 81, switch 59, conductor 80, winding 58 of the contactor 5?, resistor 81 and conductor 41 to line conductor 48 to thereby connect the winding 58 across the line conductors 38 and 48 for energizing the winding 58. Such energization of the winding 58 effects the movement of a pair of contact members 62 and 63 of the contactor 51 to circuit interrupting and circuit closing positions, respectively. Movement of contact member 82 to a circuit interrupting position interrupts a signal circuit extending from line conductor 35 through conductor 64, signal device '24, contact member 82 and conductor to line conductor 48 to thereby maintain the signal device 24 in an inoperative condition until predetermined operating conditions of the transformer I effect the energiza tion thereof. Movement of contact member 63 to a circuit closing position establishes a circuit extending from line conductor 36 through conductors 53 and 68, contact member 63, conductor 61, winding 58 of the contactor 5T, resistor 6i and conductor 41 to line conductor 48 to there by maintain the energization of the winding 58 of the contactor 51 until such time when operating conditions of the transformer l effect deenergization of the winding 58 for effecting the energization of the signal device 24 by means of an operation which will be described hereinafter.

In order to effect the deenergization of the contactor 51, the pivotally mounted switch operating member 42 is disposed to be actuated by a further predetermined movement of the bimetal 28 to the right for effecting movement of the free end of the member 42 to the left. A contact member 68 carried by the pivoted member 42 at the free end thereof is thereby moved into engagement with a fixed contact member 69. The engagement of contact members 68 and 89 establishes a circuit extending from power line conductor 38 through conductors 53 and 88, contact member 63 normally disposed in the circuit closing position as described hereinbefore, conductors 61 and I8, closed contact members 68 and 69, conductor H, resistor BI and conductor 41 to power line conductor 48. This circuit is disposed for shunting the normally energized winding 58 of the contactor 51 to effect the deenergization of the winding 58, thereby causing contact members 63 and 62 to drop to circuit interrupting and circuit closing positions, respectively. Movement of contact member 62 to the circuit-closing position establishes the signal circuit for energizing the signal device 24, and movement of the contact member 63 to the circuit interrupting position interrupts the energizing circuit for the energizing winding 58 of the contactor 51 to thereafter maintain the deenergization of the winding 58 and the energization of the signal device 24. When it is desired to deenergize the signal device 24, the switch 59 may be manually actuated to the circuit closing position as was described hereinbefore.

A brief description of operation of the protective device will serve to illustrate the advantages thereof. Assuming that the transformer load has increased to a value slightly above the rated. full load value of the apparatus and that the protective device is properly set up for normal operation, that is, the automatic-manual switch 38 has been manuall actuated to the automatic position and the start-reset switch 58 has been manually actuated to a position for energizing the winding 58 of the contactor 51, the winding 32 of the relay 33 is so energized by a current flowing therethrough which is proportional to the load current of the transformer I as to actuate the contact member 35 to a circuit closing posimovement of the bimetal element 28 to- "arl switch operating member 3! for en.- cnt therewith to move the contact memnto engagement with the contact member thereby establishing the energizing circuit for the winding 45. Such operation effects the movement 1 C ac m Advantages of protective means are apcircuit closin positions parent from the description of operation of the c ho e oe ice. For example, if it be so desired, a transas d the enere l for may be operated under overload condi- 52. respectively. 5 tio s ior a considerable time without danger of ts the 8 t l' 52 1363115 operation, the fan overheating the coil assembly. Such op ration 15 is rotated thereby for forcing air currents upis magic possible by means of operation of the from t e musing 3 into 6 Casing of control device and the protective circuits asc- 01 device to thereby effect coolil'igi sociated t1 erewith t perate th fgm 19 for of th; olmetel e e 23 y thermal 56 0 13 COOIZllg the coil assembly when the load becomes moving the bimetal 28 away from the member excessive The holding Circuit for t winding 5! whereby the contact in ber 43 is actuated to of th t go 43 i ,joged f m int ina circuit int tion. The for.- motor in operation the fan motor 52 in pcnrlently of the position of the bimetai element 28 to pres-- l5 vent a rapid. cycl 1g or hunting the fun I!) M on. of the of by alternating movement of the bimetal contractor 0 L11 i mai:n neducng: the switching duty on the t for the fan motor 57? I, mbers and increasing the efficiency of If the fan I9 fails to inefiiciently, or if the contector 57 be- ;zy means re of the now signal device 24 is encr A to or of the fa aims in such c i establishes t winding H: tain the inclepe nient When the c decreases to winding or .j to actuate the co interrupting positio circuit for the i1 thus causing U115 thereof to drop i or into to warn of ,ure of the ution until 3/ actuated l9 may be ime. if so do; by; manual ii) in the event of failure of tizsociated with the circuit 0ps itch 38. inustrtztcd r be made within the spirit of ing: the 5. contact men it .h

,i Jed c cont-act l mbers EB and es the circuit, I claim as my invention:

It, In electrical apparatus, the combination of 3 housing, a transformer core and coil assembly disposed therein, air cooling means disposed for operation to effect the cooling of the coil asc mbly, a signalling means disposed for operation 1 indicatim a predetermined overload operating e: ercondition of the transformer, a control device disi Llteneous' for the m ruptin and. establish the p'seo to be operated in response to predetermined temperatures of air currents rising from the coil assembly and, predetermined heating effects oi oi) rent flowing through the coils of the transfo mer, the control device including a thermally responsive means disposed for movement through two switching positions in response to variations in. said temperatures and heating effects, a relay disposed to be energized in response to a prede" 2d reveals to the transfori load should. be rccl be disconnected. f

should the s inoperat '3 only by manual the stir h to the r which termined flow of current through the coils and to em be deenereizerl when the current flow through t t m the coils decreases to a value below said prede- Ousiy to termine-ci flow of current, a contact member disit, and posed. to be to r.v circuit closing position for m b respectively. upon. the occurrence of a predetermined move- If it s found. n cessary perate the Zfi merit of the thermally responsive means to one ituetion such as, for example, of said switching positions, a cooling" means con- '5' tactor disposed to be energized to effect the operation of the cooling means only after the relay st or the in device it. the autocratic-menu 1 switch 3 may is energized and said contact member is actuated be manually actuated to a posit n where it 821- to circuit closing position, the relay when energaees a fixed contact member "42. Such actuagized cooperating with said contactor to theretion of the switch 38 effects the establis 'ient after effect the energization of the cooling means of a circuit extending from power line conductor independently of movement of the thermally re- 35 through conductor 3'1, switch 38, conductor sponsive means and when cleenergized cooperat- 73, winding 45 of the contactor 5-6 and conductor ing with said contactor to deenergize the coolll to line conductor 48 to thereby energize the ing means, another contact member disposed to r no for eflecting the establishment of be actuated upon the occurrence of a further prewindi J m v the energizing circuit for the fan motor :22. determined movement of the thermally responsive means to the other of said switching positions, a normally energized signalling contactor disposed for operation in response to the actuation of said another contact member to effect the operation of the signalling means, said another contact member being disposed when actuated to effect the deenergization of the signalling contactor to thereby efiect the operation of the signalling means independently of further movement of the thermally responsive means, and switch means disposed to be manually actuated for operation to energize the signalling contactor to effect the discontinuation of operation of the signalling means.

2. In electrical apparatus, the combination of a housing, a transformer core and coil assembly disposed therein, air cooling means disposed for operation to efiect the cooling of the coil assembly, a signalling means disposed for operation for indicating a predetermined overload operating condition of the transformer, a control device disposed to be operated in response to predetermined temperatures of air currents rising from the coil assembly and predetermined heating eifects of current flowing through the coils of the transformer, the control device including a thermally responsive means disposed for movement through two switching positions in response to variations in said temperatures and heating effects, a relay disposed to be energized in response to a predetermined fiow of current through the coils and to be deenergized when the current flow through the coils decreases to a value below said predetermined flow of current, a contact member disposed to be actuated to a circuit closing position upon the occurrence of a predetermined movement of the thermally responsive means to one of said switching positions, a cooling means contactor disposed to be energized to eifect the operation of the cooling means only after the relay is energized and said contact member is actuated to circuit closing position, the relay when'energized cooperating with said contactor to thereafter effect the energization of the cooling means independently of movement of the thermally responsive means and when deenergized cooperating with said contactor to deenergize the cooling means, another contact member disposed to be actuated upon the occurrence of a further predetermined movement of the thermally responsive means to the other of the switching positions, a normally energized signalling contactor disposed for operation in response to the actuation of said another contact member to effect the operation of the signalling means, said another contact member being disposed when actuated to effect the deenergization of the signalling contactor to thereby effect the operation of the signalling means independently of further movement of the thermally responsive means, switch means disposed to be manually operated to control the energization of the cooling means contactor independently of the energization of the relay and the actuation of said contact member, and another switch means disposed to be manually actuated for operation to energize the signalling contactor to effect the discontinuation of operation of the signalling means. i

3. In electrical apparatus, the combination of a housing, a transformer core and coil assembly disposed therein, air cooling means disposed-for operation to effect the cooling of the coil assembly, a signalling means disposed for operation for indicating a predetermined overload operating condition of the transformer, a control device disposed to be operated in response to predetermined temperatures of air currents rising from the coil assembly and predetermined heating effects of current flowing through the coils, the control device including a thermally responsive means disposed for movement through a two switching positions in response to variations in said temperatures and heating eifects, a relay disposed to be energized in response to a predetermined fiow of current through the coils and to be deenergized when the current flow through the coils decreases to a value below said predetermined flow of current, a contact member disposed to be actuated to a circuit closing position upon the occurrence of a predetermined movement of the thermally responsive means to one of said switching positions, a contactor disposed to be energized to effect the operation of the cooling means only after the relay is energized and said contact member is actuated to circuit closing position, the relay when energizedcooperating with said contactor to thereafter'effect the energization of the cooling means independently of movement of the thermally responsive means and when deenergized cooperating-with said contactor to deenergize to cooling means, another contact member disposed to be actuated to a circuit closing position upon the occurrence of a further predetermined movement of the thermally responsive means to the other of said switching positions, and a signalling contactor disposed for operation in response to the actuation of said another contact member to effect the operation of the signalling means.

ARTHUR V. HUGHES.

References Cited in the file of this patent An Automatic Watchman for Air-Cooled Transformers, Nov. 1944, issue of Westinghouse Engineer."

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